function $(id) {
    return typeof id === 'string' ? document.getElementById(id) : id;
}

window.onload = tab;

function tab() {
    // 当前高亮显示的页签的索引
    var index = 0;
    var timer = null;

    // 获取所有的页签和要切换的内容
    var lis = $('notice-tit').getElementsByTagName('li');
    var divs = $('notice-con').getElementsByTagName('div');
    // 遍历每一个页签且给他们绑定事件
    for (var i = 0; i < lis.length; i++) {
        lis[i].id = i;
        lis[i].onmouseover = function() {
            clearInterval(timer);
            changeOption(this.id);
        }
        lis[i].onmouseout = function() {
            timer = setInterval(autoPlay, 2000);
        }
    }

    if (timer) {
        clearInterval(timer);
        timer = null;
    }
    // 添加定时器，改变当前高亮的索引
    timer = setInterval(autoPlay, 2000);

    function autoPlay() {
        index++;
        if (index >= lis.length) {
            index = 0;
        }
        changeOption(index);
    }

    function changeOption(curIndex) {
        for (var j = 0; j < lis.length; j++) {
            lis[j].className = '';
            divs[j].style.display = 'none';
        }
        // 高亮显示当前页签
        lis[curIndex].className = 'select';
        divs[curIndex].style.display = 'block';
        index = curIndex;
    }
}